function plot_symmetric(x, y, style, symmetry)
    xs = [-rot90(x, 2); x];
    if (strcmp(symmetry, 'even'))
        sign = 1;
    elseif (strcmp(symmetry, 'odd'))
        sign = -1;
    else
        error('');
    end
    ys = [sign*rot90(y, 2); y];
    plot(xs, ys, style);
end
